公开(公告)号：US20190119770A1

公开(公告)日：2019-04-25

申请号：US16094323

申请日：2017-04-20

Applicant: POSCO ,  POSTECH ACADEMY-INDUSTRY FOUNDATION

Inventor： Joo-Hyun RYU ,  Nack-Joon KIM ,  Sung-Hak LEE ,  Won-Hwi LEE ,  Kyoo-Young LEE ,  Sea-Woong LEE

IPC: C21D8/02 ,  C22C38/02 ,  C22C38/04 ,  C22C38/06 ,  C22C38/00 ,  C22C38/12 ,  C22C38/14 ,  C23C2/28 ,  C23C2/06 ,  C23C2/02 ,  C23C2/40 ,  C21D9/46

Abstract: Provided is an ultrahigh-strength steel sheet for a vehicle and, more specifically, to an ultrahigh-strength and high-ductility steel sheet having excellent yield ratio and a manufacturing method therefor. Provided is an ultrahigh-strength and high-ductility steel sheet for cold press forming and a manufacturing method therefor, the steel sheet ensuring ultrahigh strength and high ductility since an alloy component of steel and manufacturing conditions are controlled and, simultaneously, having excellent impact characteristics due to a high yield strength ratio (yield ratio). Provided is the steel sheet capable of satisfying formability and impact stability, which are required for a vehicle steel sheet for cold forming, and replacing a conventional steel sheet for hot press forming, thereby reducing manufacturing costs.

公开(公告)号：US20200157649A1

公开(公告)日：2020-05-21

申请号：US16629757

申请日：2018-04-12

Applicant: POSCO ,  POSTECH ACADEMY-INDUSTRY FOUNDATION

Inventor： Sung-Hak LEE ,  Kyoo-young LEE ,  Joo-Hyun RYU ,  Sea-Woong LEE ,  Seok-Su SOHN ,  Hyung-Soo LEE ,  Min-Chul JO

IPC: C21D9/46 ,  C22C38/12 ,  C22C38/06 ,  C22C38/04 ,  C22C38/02 ,  C22C38/00 ,  C21D8/02 ,  C21D6/00

Abstract: Provided is a hot rolled steel sheet having excellent strength and elongation. The hot rolled steel sheet contains, by wt %: carbon (C): 0.05% or more and less than 0.4%, manganese (Mn): 10% to 15%, aluminum (Al): 2% or less, silicon (Si): 0.1 to 2%, molybdenum (Mo): 0.5% or less (excluding 0), vanadium (V): 0.5% or less (excluding 0), phosphorus (P): 0.01% or less, sulfur (S): 0.01% or less, and a remainder of iron (Fe) and inevitable impurities. The hot rolled steel sheet has a microstructure of the hot rolled steel sheet containing, by area %, tempered martensite: 50% to 70%, secondary martensite: 20% or less (excluding 0), epsilon martensite: 2% or less (excluding 0), and retained austenite: 8% to 30%. The hot rolled steel sheet has a tensile strength of at least 1500 MPa, a yield strength of at least 900 MPa and elongation of at least 20%.